My guess from the bottom jaws and the handle is a Sq D XO style breaker.
Just a guess.
Alan--

Well, I guess I can start here, and hopefully others can add a lot to this.

Square D and Cutler Hammer produced millions of these "XO" style circuit breakers many years ago. I'm guessing that this was among the first efforts to market a single interchangeable breaker (as opposed to the "multi-breaker design"). The panel in which these breakers were installed was rated for 120/240 volt service, and had two bus bars mounted on an insulated base which extended nearly the entire interior length of the box (along with a neutral buss, of course). The XO breaker simply clipped onto the bus bars. On single pole breakers, the brighter-colored clip, shown in the second photo, tapped the current from the bus bar, while the other clip was merely a dummy. It had no internal connection, and only served to help hold the breaker in place inside the panel. The load on the panel was balanced by installing breakers with the current tap alternating between left and right busses. A double pole breaker was manufactured as a one-piece unit with two clips arranged to tap both bus bars.

In my part of the world where I live, there are many of these breakers and panels still in service. These breakers are routinely listed for sale on eBay (though I'm not so sure how good an idea it is to purchase a used circuit breaker from any source - at least with the intent of re-use).

Mike (mamills)

Cliff,
That "stiff card-board" wouldn't happen to be mica would it?
Or something mica-based?.
It's used in toasters to hold the nichrome elements in place and makes a pretty good insulator that can withstand quite a bit of heat (handy in a toaster).
I have some mis-givings about CB's that merely clip onto busbars, as in I feel that the connection can never be as good as a solid screwed connection or the like.
Has there ever been a problem with the joint between clip and busbar ever overheating when a lot of current is drawn through the breaker?.
Just inquisitive.

XO's were always copper bussed (some were plated too).The big problem w/ XO's were having to alternate breakers on buss bars* and they were not "trip free".

* Same thing has/had to be done w/ single pole full size Zinsco breakers (remove clip and alternate them ) otherwise they would be all on same leg in panel.

Mike: I have seen a number of these panels over the years, both in service and removed from service (with a few in my collection). The only damage I can ever recall was to the load screw terminal of one 20 amp. circuit breaker, the result of some clown's poor attempt to lug three wires to it. The busses and breaker clips were just about as shiny as new - no evidence of arcing, pitting, burning, etc. Seems the clips used to fit pretty tightly around the busses.

Mike (mamills)

The 'stiff cardboard' is likely made of layers of paper, impregnated with phenolic resins. Not a whole lot different from the stuff Formica counter tops are made of.

Here are a few more pics, of similar breakers:

First, from Norcal, is the breaker and it's packaging:





I recently came across these on a job. The panel looks like this, all closed up:





Notice how the handles seem to be 'all over the place?' Every breaker in that pic is "on." A look inside reveals what is 'strange' here:





There is but a single column of breakers. You decide which buss is used by flipping the breaker over.

The breaker pictured is a bit rare, if you look at the one in the rear, it takes 3 pole spaces, the one in front uses only 2 spaces.The one in the rear is a 20 or 30 A breaker and is a lot more common.

I see 2 wires (12 or 14 AWG) that are connected to the main busses without any OCP other than that provided by the main breaker.

2-Pole breaker (5th/6th down from top) also appears to have an empty lug.

Hi guys: I would like to ask one question about these two-pole breakers. The handles are "tied" together with a small piece of stiff wire that appears to be inserted in the open space in the two handles before the whole affair is assembled (and operates with a sorta sloppy movement from off to on and vice versa). Do these two halves of the double pole breaker operate as a common trip, i.e. a fault in either leg will cause both to open?

My reason for asking is that I have seen some of these double pole breakers that, for whatever reason, are missing the little handle tie and appear to function as nothing more than two separate single pole breakers (even though they are constructed as a two pole unit).

Mike (mamills)

At the risk of offending (please forgive me), it looks as though there are three breakers (well painted at that, unfortunately) that appear to be "off"- the ones with an X on them.

Wa2wise, mamills ... Great catches.

The breakers with the "x" marks are, in fact, off while I worked on those circuits. One of the circuits mysteriously stopped supplying power to the entire run, and all three were in the same pipe. You caught me working ... and doing so safely ... don't let anyone find out!

As for the small wires double-lugged to the mains ... by golly, you're right. I was so focused on the trees, I failed to see the forest. I was wondering what I would do for work Monday; now I have a customer to call upon.

I believe the black 'papery' material is likely vulcanized fiber or slang; "fish paper."

I've found that the stuff is only marginally water resistant, loosing its insulating quality with exposure to water or high humidity.

See: www.jjorly.com/fish_paper_die_cut.htm